Merge #390

390: internals: sigmatch comments and code style r=saem a=saem

## Summary
No behaviour changes, a few things should be more clear.

## Details
Added some `ast.newSymNode` overloads for convenience.


Co-authored-by: saem <saemghani+github@gmail.com>

compiler/ast/ast.nim

@@ -200,17 +200,18 @@ proc newSymNode2*(sym: PSym, info: TLineInfo): PNode =
     result.typ = sym.typ
     result.info = info
 
-proc newSymNode*(sym: PSym): PNode =
-  result = newNode(nkSym)
+proc newSymNodeIT*(sym: PSym, info: TLineInfo, typ: PType): PNode =
+  ## create a new sym node with the supplied `info` and `typ`
+  result = newNodeIT(nkSym, info, typ)
   result.sym = sym
-  result.typ = sym.typ
-  result.info = sym.info
 
-proc newSymNode*(sym: PSym, info: TLineInfo): PNode =
-  result = newNode(nkSym)
-  result.sym = sym
-  result.typ = sym.typ
-  result.info = info
+proc newSymNode*(sym: PSym, info: TLineInfo): PNode {.inline.} =
+  ## create a new sym node from `sym` with its type and supplied `info`
+  result = newSymNodeIT(sym, info, sym.typ)
+
+proc newSymNode*(sym: PSym): PNode {.inline.} =
+  ## create a new sym node from `sym` with its info and type
+  result = newSymNode(sym, sym.info)
 
 proc newIntNode*(kind: TNodeKind, intVal: BiggestInt): PNode =
   result = newNode(kind)

compiler/ast/types.nim

@@ -1163,13 +1163,20 @@ proc skipConvTakeType*(n: PNode): PNode =
   result.typ = n.typ
 
 proc isEmptyContainer*(t: PType): bool =
+  ## true if the type is considered a container and is empty, otherwise false.
+  ## container types are untyped, nil, `array/seq/set/etc[T]` with an emtpy
+  ## type for `T`.
   case t.kind
-  of tyUntyped, tyNil: result = true
-  of tyArray: result = t[1].kind == tyEmpty
+  of tyUntyped, tyNil:
+    true
+  of tyArray:
+    t[1].kind == tyEmpty
   of tySet, tySequence, tyOpenArray, tyVarargs:
-    result = t[0].kind == tyEmpty
-  of tyGenericInst, tyAlias, tySink: result = isEmptyContainer(t.lastSon)
-  else: result = false
+    t[0].kind == tyEmpty
+  of tyGenericInst, tyAlias, tySink:
+    isEmptyContainer(t.lastSon)
+  else:
+    false
 
 proc takeType*(formal, arg: PType; g: ModuleGraph; idgen: IdGenerator): PType =
   # param: openArray[string] = []